Making AI avoid obstacles and make it wander?

Hi, I'm trying to understand some scripts and make a basic game.

Here's what I got:

var target : Transform; var moveSpeed = 0; var rotationSpeed = 3; var player : Transform; var distance: float = 5.8; var distanceAttack:float = 2.6; var myTransform : Transform; function Awake() { myTransform = transform; }

 function Start() {
 animation.Play("idle");
 target = GameObject.FindWithTag("Player").transform;
 }
 function Update () {
 if(Vector3.Distance(transform.position, player.position) < distance){
 if(Vector3.Distance(transform.position, player.position) >distanceAttack){
 moveSpeed = 2;
 animation.Play("walk");
 myTransform.rotation = Quaternion.Slerp(myTransform.rotation,
 Quaternion.LookRotation(target.position - myTransform.position), rotationSpeed*Time.deltaTime);
 myTransform.position += myTransform.forward * moveSpeed * Time.deltaTime;
 Debug.DrawLine(target.position, myTransform.position, Color.red);
 }
 
 if(Vector3.Distance(transform.position, player.position) < distanceAttack){
 moveSpeed = 0;
 animation.Play("attack");
 }
 }
 else{
 moveSpeed = 0;
 animation.CrossFade("idle");
 }
 }

So, now, I want to, when I walk behind a wall, it go around it. AND, when I'm away from it, it walk to random locations.

Please, help me... Sorry for my Enlish =/